1. Field of the Invention
The present invention relates to image formation processes and apparatus generally, and, more particularly, to developing devices and processes for electrophotographic printers, laser printers, photocopiers.
2. Description of the Related Art
Generally, an electrophotographic printer includes a developing device that transfers images from a surface of a photosensitive drum to a printable medium such as paper fed from an internal or external feed device, and a fixing roller that heats the toner forming a latent image borne by the printable medium.
Conventional electrophotographic printers use a photosensitive drum, a developing roller, and a feeding roller. There must be nips, which are contact areas, between the photosensitive drum and the developing roller, and between the developing roller and the feeding roller. To maintain these nips, the electrophotographic printer has a power transmitting gear and the timing belt. Since the developing roller and the feeding roller are directly meshed with each other, it is difficult to transmit the power at a desirable velocity ratio while maintaining their nip within an acceptable range of length.
Direct contact between the feeding roller and the developing roller induces vibration and inconsistent velocity of the feeding roller while the feeding roller is transferring the developer to the developing roller. This, in turn, causes jitter, that is, irregular gaps between dots of a latent image on the exterior cylindrical surface of the photosensitive drum, so that the best printing quality cannot be assured.
Accordingly, it is an object of the present invention to provide an improved image forming apparatus and process.
It is another object to provide an image forming apparatus having an improved arrangement of gears.
It is still another object to provide a developing device and process in an electrophotographic printer that exhibits minimal jitter.
It is yet another object to provide a developing device and process in an electrophotographic printer that reduces occurrence of vibration while maintaining constant velocity of the feeding roller.
According to the present invention, an image forming apparatus may be constructed according to the principles of the present invention with a power transmitting gear meshed with a photosensitive drum gear formed on a photosensitive drum, and a transmission belt that transmits a driving force from the power transmitting gear to a developing roller gear formed on a developing roller. The power transmitting gear is meshed with an idler gear, and the idler gear is meshed with a feeding roller gear formed on a feeding roller that feeds a developer to the developing roller. With this configuration, the power transmitting gear transfers a driving force from the photosensitive drum to the feeding roller gear.